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Meteorhead
Challenger

Webarticle about AMDs Graphics Core Next - GCN

My guess would be, that there will be a bit more processors on the die. The last fabrication process jump from 65nm to 40nm, the SIMD engines were doubled. basically two of the same chips fit into the same die. With this new architecture, a lot of new functionality has been brought (virtual address space, c++, dll, ...) but VLIW Cores were far from simple also. New functionality won't increase complexity to a degree that no additional raw power can be added.

I think there will be roughly 25% increase in the number of processors, with the increased complexity. This architecture has a big tradeoff: namely you need a lot more threads to keep it busy. Of course, that is natural if the the processors increase, but this time you need 4X more than with "traditional" VLIW. Some lattice computations are very paralell, but no more than O(1000) threads can be used at a time, meaning, that although they are computehungry, multi-gpu is hard with Cayman, but with GCN it is out of the question.

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dravisher
Journeyman III

Webarticle about AMDs Graphics Core Next - GCN

I'm not so sure that we'll need 4x as many work-items to keep it busy. With Cayman we need two wavefronts per CU, with GCN we need four wavefronts. However (in my experience) at least four wavefronts are needed per CU in Cayman/Cypress to get decent performance, and it's not entirely clear that GCN will really need any more work-items at all in practice. I've asked a question about this in the other thread (whether GCN will require more work-items to hide memory latency).

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